Over on the Light Device handler information page, a fantastic primer has been posted by @SmartHomePrimer:
From what I’ve been reading, that suggests that the device is joining the same Zigbee network, and then being used as a secondary controller (I think that’s the right Zigbee terminology). At the moment, I am waiting for the electrics in the bathroom to be sorted out (they’re MR16 not GU10), so can’t test what happens after - but I am wondering if the hub will see the commands that are sent to the lights or not, seeing as it would now be bound to the lights directly. If the hub can see the commands, you might get a much better idea of what’s going on!